Two main types of carrying structures for aerial transportation and transmission means like ski lift, tramway, freight ropeway, high voltage electricity line, etc. are used:
Type 1--a plurality of supports (usually towers) standing on the ground and spaced at a relatively small distance. The aerial means are placed on a cross beam at the top of the tower. The beam transfers all horizontal and vertical loads and torques from the aerial means to the tower. PA1 Type 2--a carrying cable suspended at its ends by any convenient way. A span of the cable is usually 8-10 times longer than the distance between the towers in (1). The aerial means are supported by a plurality of cross beams attached to the cable. Functions of these beams are similar to (1). PA1 Type 1: PA1 heights of the towers depend on a profile of the ground along a route of the aerial means and might be 200-250 ft. or even more. Cost of such towers and expenses for their erection and maintenance are very high. For profiles with depressions 400-500 ft. towers are actually, not applicable; PA1 towers can be destroyed by strong storm, snow-slip, land slide, earthquake and other natural disasters which happen in mountains rather often. A destruction of even one tower leads to destruction of the aerial means. Restoring works are very expensive. PA1 the carrying cable is subjected to horizontal displacements and rocking of the cable along it's length from one support to another. As a result, special heavy cable, or a number of cables, or a horizontal supporting means for the cable are installed. All these measures sharply increase cost of the aerial means. PA1 the carrying cable is stretched between its end supports, one end of the cable is anchored and the other is attached to a tensioning means; then, a part of the designed tensioning load, enough for stretching the unloaded cable, is applied; PA1 rigid elements with attached guy ropes and main supporting components of the aerial means, such as carrying ropes, hauling ropes, etc. are mounted on the cable and hauled one by one to their working position along the cable; PA1 the lower end of the guy ropes are attached to the anchoring means, then the guy ropes are pulled down until a projected profile of the cable above the ground is reached; PA1 the tension of the cable is gradually increased up to the design level, which also provides the increasing of tension stress in the guy ropes. The lengths of the guy ropes are adjusted, if necessary.
Both types of the carrying structures have drawbacks, especially for routes in mountains and on uneven terrain.
Type 2:
With these drawbacks, the advantages of prior art in carrying structures for the aerial means is largely offset by their disadvantages.